Biomarkers of exposure to metals and metalloids have proven to be powerful tools for epidemiologic studies that seek to study associations between exposures and human health effects. The Trace Metals Core Lab came into existence in 1994 as part of our NIEHS Center, and received a rating of outstanding at NIEHS Center site visits that occurred in 1997 and 2002. The Laboratory participates in multiple quality control programs and has an outstanding record of past performance. Biomedical research Projects #2, #3 and #4, which take place in Bangladesh and New Hampshire, propose to test a set of novel hypotheses concerning the mechanisms and effects of exposure to As and Mn from drinking water. These projects collectively require the analysis of more than 60,000 biological specimens;this estimate approximates the total of 70,000 specimens that have been successfully measured during the past five years. The biological specimens to be analyzed and stored in the Trace Metals Core Lab include blood, urine and toenails. The methodologies employed will include graphite furnace atomic absorption spectrophotometry (GFAAS) (e.g., arsenic in urine and lead in blood), inductively-coupled plasma mass spectrometry with dynamic reaction cell (ICP-MS-DRC) (e.g., total As, Mn and Se in blood), HPLC coupled to ICP-MS-DRC (e.g., arsenic metabolites in urine and blood), and ELISA technology (clara cell protein-16). The Trace Metals Core Laboratory is well equipped to carry out these and other requested analyses at no cost to members of this Superfund Basic Research Program.